drm/i915/gvt: Fix stack-out-of-bounds bug in cmd parser

for_each_set_bit() only accepts variable of type unsigned long, and we can
not cast it from smaller types.

[   16.499365] ==================================================================
[   16.506655] BUG: KASAN: stack-out-of-bounds in find_first_bit+0x1d/0x70
[   16.513313] Read of size 8 at addr ffff8803616cf510 by task systemd-udevd/180
[   16.521998] CPU: 0 PID: 180 Comm: systemd-udevd Tainted: G     U     O     4.15.0-rc3+ #14
[   16.530317] Hardware name: Dell Inc. OptiPlex 7040/0Y7WYT, BIOS 1.2.8 01/26/2016
[   16.537760] Call Trace:
[   16.540230]  dump_stack+0x7c/0xbb
[   16.543569]  print_address_description+0x6b/0x290
[   16.548306]  kasan_report+0x28a/0x370
[   16.551993]  ? find_first_bit+0x1d/0x70
[   16.555858]  find_first_bit+0x1d/0x70
[   16.559625]  intel_gvt_init_cmd_parser+0x127/0x3c0 [i915]
[   16.565060]  ? __lock_is_held+0x8f/0xf0
[   16.568990]  ? intel_gvt_clean_cmd_parser+0x10/0x10 [i915]
[   16.574514]  ? __hrtimer_init+0x5d/0xb0
[   16.578445]  intel_gvt_init_device+0x2c3/0x690 [i915]
[   16.583537]  ? unregister_module_notifier+0x20/0x20
[   16.588515]  intel_gvt_init+0x89/0x100 [i915]
[   16.592962]  i915_driver_load+0x1992/0x1c70 [i915]
[   16.597846]  ? __i915_printk+0x210/0x210 [i915]
[   16.602410]  ? wait_for_completion+0x280/0x280
[   16.606883]  ? lock_downgrade+0x2c0/0x2c0
[   16.610923]  ? __pm_runtime_resume+0x46/0x90
[   16.615238]  ? acpi_dev_found+0x76/0x80
[   16.619162]  ? i915_pci_remove+0x30/0x30 [i915]
[   16.623733]  local_pci_probe+0x74/0xe0
[   16.627518]  pci_device_probe+0x208/0x310
[   16.631561]  ? pci_device_remove+0x100/0x100
[   16.635871]  ? __list_add_valid+0x29/0xa0
[   16.639919]  driver_probe_device+0x40b/0x6b0
[   16.644223]  ? driver_probe_device+0x6b0/0x6b0
[   16.648696]  __driver_attach+0x11d/0x130
[   16.652649]  bus_for_each_dev+0xe7/0x160
[   16.656600]  ? subsys_dev_iter_exit+0x10/0x10
[   16.660987]  ? __list_add_valid+0x29/0xa0
[   16.665028]  bus_add_driver+0x31d/0x3a0
[   16.668893]  driver_register+0xc6/0x170
[   16.672758]  ? 0xffffffffc0ad8000
[   16.676108]  do_one_initcall+0x9c/0x206
[   16.679984]  ? initcall_blacklisted+0x150/0x150
[   16.684545]  ? do_init_module+0x35/0x33b
[   16.688494]  ? kasan_unpoison_shadow+0x31/0x40
[   16.692968]  ? kasan_kmalloc+0xa6/0xd0
[   16.696743]  ? do_init_module+0x35/0x33b
[   16.700694]  ? kasan_unpoison_shadow+0x31/0x40
[   16.705168]  ? __asan_register_globals+0x82/0xa0
[   16.709819]  do_init_module+0xe7/0x33b
[   16.713597]  load_module+0x4481/0x4ce0
[   16.717397]  ? module_frob_arch_sections+0x20/0x20
[   16.722228]  ? vfs_read+0x13b/0x190
[   16.725742]  ? kernel_read+0x74/0xa0
[   16.729351]  ? get_user_arg_ptr.isra.17+0x70/0x70
[   16.734099]  ? SYSC_finit_module+0x175/0x1b0
[   16.738399]  SYSC_finit_module+0x175/0x1b0
[   16.742524]  ? SYSC_init_module+0x1e0/0x1e0
[   16.746741]  ? __fget+0x157/0x240
[   16.750090]  ? trace_hardirqs_on_thunk+0x1a/0x1c
[   16.754747]  entry_SYSCALL_64_fastpath+0x23/0x9a
[   16.759397] RIP: 0033:0x7f8fbc837499
[   16.762996] RSP: 002b:00007ffead76c138 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
[   16.770618] RAX: ffffffffffffffda RBX: 0000000000000012 RCX: 00007f8fbc837499
[   16.777800] RDX: 0000000000000000 RSI: 000056484e67b080 RDI: 0000000000000012
[   16.784979] RBP: 00007ffead76b140 R08: 0000000000000000 R09: 0000000000000021
[   16.792164] R10: 0000000000000012 R11: 0000000000000246 R12: 000056484e67b460
[   16.799345] R13: 00007ffead76b120 R14: 0000000000000005 R15: 0000000000000000
[   16.808052] The buggy address belongs to the page:
[   16.812876] page:00000000dc4b8c1e count:0 mapcount:0 mapping:          (null) index:0x0
[   16.820934] flags: 0x17ffffc0000000()
[   16.824621] raw: 0017ffffc0000000 0000000000000000 0000000000000000 00000000ffffffff
[   16.832416] raw: ffffea000d85b3e0 ffffea000d85b3e0 0000000000000000 0000000000000000
[   16.840208] page dumped because: kasan: bad access detected
[   16.847318] Memory state around the buggy address:
[   16.852143]  ffff8803616cf400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   16.859427]  ffff8803616cf480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1
[   16.866708] >ffff8803616cf500: f1 f1 04 f4 f4 f4 f3 f3 f3 f3 00 00 00 00 00 00
[   16.873988]                          ^
[   16.877770]  ffff8803616cf580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   16.885042]  ffff8803616cf600: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
[   16.892312] ==================================================================

Signed-off-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/cmd_parser.c

@@ -2777,12 +2777,12 @@ int intel_gvt_scan_and_shadow_wa_ctx(struct intel_shadow_wa_ctx *wa_ctx)
 }
 
 static struct cmd_info *find_cmd_entry_any_ring(struct intel_gvt *gvt,
-		unsigned int opcode, int rings)
+		unsigned int opcode, unsigned long rings)
 {
 	struct cmd_info *info = NULL;
 	unsigned int ring;
 
-	for_each_set_bit(ring, (unsigned long *)&rings, I915_NUM_ENGINES) {
+	for_each_set_bit(ring, &rings, I915_NUM_ENGINES) {
 		info = find_cmd_entry(gvt, opcode, ring);
 		if (info)
 			break;